/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Deque;
import java.util.Iterator;

/**
 * A deque which forwards all its method calls to another deque. Subclasses should override one or
 * more methods to modify the behavior of the backing deque as desired per the
 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p>
 * <b>Warning:</b> The methods of {@code ForwardingDeque} forward <b>indiscriminately</b> to the
 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
 * behavior of {@link #offer} which can lead to unexpected behavior. In this case, you should
 * override {@code offer} as well.
 *
 * <p>
 * <b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingDeque}.
 *
 * @author Kurt Alfred Kluever
 * @since 12.0
 */
@GwtIncompatible
public abstract class ForwardingDeque<E> extends ForwardingQueue<E> implements Deque<E> {

    /** Constructor for use by subclasses. */
    protected ForwardingDeque() {}

    @Override
    protected abstract Deque<E> delegate();

    @Override
    public void addFirst(E e) {
        delegate().addFirst(e);
    }

    @Override
    public void addLast(E e) {
        delegate().addLast(e);
    }

    @Override
    public Iterator<E> descendingIterator() {
        return delegate().descendingIterator();
    }

    @Override
    public E getFirst() {
        return delegate().getFirst();
    }

    @Override
    public E getLast() {
        return delegate().getLast();
    }

    @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
    @Override
    public boolean offerFirst(E e) {
        return delegate().offerFirst(e);
    }

    @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
    @Override
    public boolean offerLast(E e) {
        return delegate().offerLast(e);
    }

    @Override
    public E peekFirst() {
        return delegate().peekFirst();
    }

    @Override
    public E peekLast() {
        return delegate().peekLast();
    }

    @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
    @Override
    public E pollFirst() {
        return delegate().pollFirst();
    }

    @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
    @Override
    public E pollLast() {
        return delegate().pollLast();
    }

    @CanIgnoreReturnValue
    @Override
    public E pop() {
        return delegate().pop();
    }

    @Override
    public void push(E e) {
        delegate().push(e);
    }

    @CanIgnoreReturnValue
    @Override
    public E removeFirst() {
        return delegate().removeFirst();
    }

    @CanIgnoreReturnValue
    @Override
    public E removeLast() {
        return delegate().removeLast();
    }

    @CanIgnoreReturnValue
    @Override
    public boolean removeFirstOccurrence(Object o) {
        return delegate().removeFirstOccurrence(o);
    }

    @CanIgnoreReturnValue
    @Override
    public boolean removeLastOccurrence(Object o) {
        return delegate().removeLastOccurrence(o);
    }
}
